According to Patent Literature 1, melt-processable polytetrafluoroethylene is produced in the presence of ammonium perfluorohexanoate. However, since a large amount of ammonium persulfate is used in the presence of ethane, polymeric non-melt-processable PTFE cannot be produced under this condition.
Patent Literature 2 discloses an aqueous dispersion of polytetrafluoroethylene produced by polymerization in the presence of ammonium perfluorooctanoate and ammonium perfluoroheptanoate.
Patent Literature 3 discloses a method for polymerizing fluorine-containing monomers in an aqueous medium containing an initiator and a polymerization aid, wherein the polymerization aid includes a combination of a fluoropolyether acid having a number average molecular weight of 800 g/mol or more and a fluorochemical surfactant.
Patent Literature 4 discloses a method for producing a polytetrafluoroethylene aqueous emulsion containing 0.001 to 0.01% by mass, based on the amount of produced polytetrafluoroethylene, of a comonomer having a monomer reactivity ratio of 0.1 to 8 in copolymerization with tetrafluoroethylene, in the presence of a C4-C8 fluorine-containing carboxylic acid having 1 to 4 ether oxygen atoms in a main chain and its salt.